The present invention relates to a front end loading interface used in the loading of workpieces in semiconductor processing equipment.
Semiconductor processing equipment often has a plurality of chambers in which processing occurs. Arm assemblies or other robotic devices are generally used to move workpieces, generally wafers from a wafer queuing station to various chambers for processing. When the processing is finished the wafer is returned to the queuing station. For an example of prior art processing equipment, see U.S. Pat. No. 4,715,921 issued to Maher et al. for a Ouad Processor.
Semiconductor processing is typically done in a vacuum. Therefore, a wafer queuing station into which is placed a cassette of wafers to be processed must be pumped down before the wafers may be accessed. This significantly increases the time the semiconductor processing equipment is idle while waiting for a cassette of processed wafers to be exchanged for a cassette of unprocessed wafers and subsequent pumping down of the wafer queuing station.
In accordance with the preferred embodiment of the present invention, a workpiece loading interface is presented for inclusion within a workpiece processing system. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of workpieces, typically wafers, from a first chamber are being accessed, a second cassette of wafers may be loaded in the second chamber and the second chamber may then be pumped down. This can significantly increase throughput of wafers through the workpiece processing system.
In the preferred embodiment, each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette of wafers is on a support with no side panels, facilitating the replacement of a cassette of processed wafers with a cassette of unprocessed wafers by an automated device. The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.